Single-voxel Magnetic Resonance Spectroscopy Research Articles

The Circulatory Arrest Recovery Ammonia Problem (CARAP) Hypothesis: a 1H-MRS study of brain metabolism during neonatal cardiopulmonary bypass surgery.

Congenital heart disease affects 1% of US births, with many babies requiring major cardiothoracic surgery under cardiopulmonary bypass (CPB), exposing the more critical patients to neurodevelopmental impairment. Optimal surgical parameters to minimize neuronal injury are unknown. We used 1H MRS and blood ammonia assays in a neonatal pig model of CPB to compare two approaches, complete circulatory arrest (CA) versus antegrade cerebral perfusion (ACP). Two-week old piglets (N=17) were put on a CPB pump and placed in a 3T MRI to study brain metabolism during CPB. Dynamic single-voxel 1H MRS brain data were acquired while animals underwent one of four CPB protocols: ∼50 min CA at 18ºC and 28ºC or ACP at 18ºC and 28ºC, followed by a ∼1-hr recovery period. Based on 1H MRS findings suggesting the presence of brain ammonia upon reperfusion, a second cohort of piglets (N=22) underwent the same CPB conditions without MRS to allow regular venous blood sampling with ammonia assays. All animals showed a transitory temperature-dependent rise in blood ammonia (p < .001) immediately following restart of whole-body perfusion . In contrast, metabolic processing of brain ammonia, as detected by an increased 1H MRS glutamine/glutamate ratio, was also temperature dependent (p =.002) but only significantly observed in the CA studies (p =.009). Serial 1H-MRS and blood ammonia assays in this preclinical CPB model identified a previously unreported build-up of ammonia, hypothesized to arise from gut bacterial production, following reperfusion, that may contribute to brain injury in these pediatric surgeries.

NIMG-56. MAGNETIC RESONANCE SPECTROSCOPY IN THE POST-TREATMENT METABOLIC CHARACTERIZATION OF BRAIN TUMORS OF GLIAL ORIGIN OF CENTRAL NERVOUS SYSTEM

Abstract BACKGROUND and Purpose Central Nervous System tumors have a very low incidence worldwide, however they constitute an important source of mortality and morbidity. Treatment for these types of tumors in adults may include surgery, radiosurgery, radiation therapy, chemotherapy, and targeted treatment. These treatments in brain tumors of glial origen in adults can produce changes in the pathophysiology of the tumor. The purpose of this study was to characterize the different metabolic patterns as effect of treatment and identify tumor recurrences. Materials and METHODS A prospective study was conducted with patients with low- and high-grade tumors treated, subjecting them to the single-voxel MRS and multivoxel MRSI protocol at 1.5 T. RESULTS Of the 44 patients included, 21 were histopathologically diagnosed as low-grade tumors and 23 as high-grade tumors. Of the low-grade tumors, 11 were caracterized as low-grade (mean Cho/NAA and NAA/Cr ratios 1.49 ((p=0.036) and 0.92 (p=0.038) respectively), 8 cases presented gliosis (mean Cho/NAA and NAA/Cr ratios 1.57 (p=0.028) and 1.36 (p=0.026) respectively), and 4 cases presented radiation necrosis (mean Cho/Cr ratios 2.14 (p=0.03)), (mean Cho/Cr and NAA/Cr ratios 1.25 (p=0.01) and 1.25 (p=0.00)) respectively). Furthermore, tumor recurrence that presented high Cho/NAA ratio were observed in 11 cases. Of the high-grade tumors, 13 were caracterized as high-grade (mean Cho/NAA and Cho/Cr ratios 2.24 (p=0.026) and 4.48 (p=0.026) respectively), 13 cases presented gliosis (mean Cho/NAA and NAA/Cr ratios 1.82 (p=0.028) and 0.64 (p=0.026)) respectively) and radiation necrosis was detected in 10 cases (mean Cho/Cr ratio 1.47 (p=0.03), (mean Cho/Cr and NAA/Cr ratios 2.25 (p=0.01) and 0.97 (p=0.00) respectively). Moreover, tumor recurrence that presented high Cho/NAA ratio were observed in 9 cases. CONCLUSION MRS and MRSI contribute to identifying the recurrences, to characterizing the different metabolic patterns as an effect of the treatment and differentiate between low and high grade tumors.

CHARACTERISATION OF THE RESPONSE OF PRE-CLINICAL MODELS OF GLIOMA TO METABOLIC THERAPIES USING IN VIVO MAGNETIC RESONANCE SPECTROSCOPY

Abstract AIMS Magnetic resonance imaging (MRI) is routinely used to diagnose and monitor brain tumours. Magnetic resonance spectroscopy (MRS) allows us to record the metabolic profile of tumours in situ. This provides a non-invasive method to monitor the response of tumours to metabolic therapies. We aimed to characterise the response of pre-clinical models of glioma to metabolic therapies such as arginine deprivation and the ketogenic diet (KD) by MRS, to better understand what metabolic changes are occurring in the tumour. METHOD We performed orthotopic injection of three different cell lines, including the syngeneic models GL261 and CT2A, as well as a primary GBM cell line, into the striatum of C57BL/6 and athymic nude mice respectively. Mice were randomised to either arginine deprivation treatment using pegylated arginine deiminase (ADI), or KD, plus controls. In each animal, we collected single voxel MRS data using STEAM on both the tumour itself, and healthy brain. MRS data was exported in jMRUI format and analysed in R using the spant package, followed by PCA and OPLS-DA. RESULTS PCA showed that there is clear distinction between healthy and tumour spectra across all models. OPLS-DA indicated that the lipid and choline spectral regions were significantly associated with tumour, whereas the NAA and glutamine/glutamate regions were significantly associated with healthy brain. Integration of specific peaks associated with these metabolites confirmed these results. Subset analysis indicated distinct metabolic signatures between the syngeneic models and the primary GBM model. Furthermore, there is evidence to suggest that tumours in animals treated with arginine deprivation have a unique metabolic signature. CONCLUSION This data indicates that the tumour specific response to metabolic therapies can be measured by routine MRS screening. This would allow a non-invasive method by which clinicians could monitor the effectiveness of metabolic therapies in patients with gliomas.

On the impact of B0 shimming algorithms on single-voxel MR spectroscopy.

To assess the impact of different B0 shimming algorithms on MRS. B0 field maps and single-voxel MR spectroscopy were acquired in the prefrontal cortex of five volunteers at 3 T using five different B0 shimming approaches. B0 shimming was achieved using Siemens' proprietary shim algorithm, in addition to the Pseudo-Inverse (PI), Quadratic Programming (QuadProg), Least Squares (LSq), and Gradient optimization (Grad) algorithms. The standard deviation of the shimmed B0 field, as well as the SNR and FWHM of the measured metabolites, was used to evaluate the performance of each B0 shimming algorithm. Compared to Siemens's shim, significant reductions (p < 0.01) in the standard deviation of the B0 field distribution within the MRS voxel were observed for the PI, QuadProg, and Grad algorithms (3.8 Hz, 7.3 Hz, and 3.9 Hz respectively, compared to 11.5 Hz for Siemens), but not for the LSq (12.9 Hz) algorithm. Moreover, significantly increased SNR and reduced FWHM for the N-acetylaspartate metabolite were consistent with the improvement in B0 homogeneity for the aforementioned shimming algorithms. Here, we demonstrate that the choice of B0 shimming algorithm can have a significant impact on the quality of MR spectra and that significant improvements in spectrum quality could be achieved by using alternatives to the default vendor approach.

A Multimodal Magnetic Resonance Imaging Study on Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Feasibility and Clinical Correlation.

Background/Objectives: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a neurological disorder characterized by post-exertional malaise. Despite its clinical relevance, the disease mechanisms of ME/CFS are not fully understood. The previous studies targeting brain function or metabolites have been inconclusive in understanding ME/CFS complexity. We combined single-voxel magnetic resonance spectroscopy (SV-MRS) and functional magnetic resonance imaging (fMRI). Our objectives were to examine the feasibility of the multimodal MRI protocol, identify possible differences between ME/CFS and healthy controls (HCs), and relate MRI findings with clinical symptoms. Methods: We enrolled 18 female ME/CFS participants (mean age: 39.7 ± 12.0 years) and five HCs (mean age: 45.6 ± 14.5 years). SV-MRS spectra were acquired from three voxels of interest: the anterior cingulate gyrus (ACC), brainstem (BS), and left dorsolateral prefrontal cortex (L-DLPFC). Whole-brain fMRI used n-back task testing working memory and executive function. The feasibility was assessed as protocol completion rate and time. Group differences in brain metabolites and fMRI activation between ME/CFS and HCs were compared and correlated with behavioral and symptom severity measurements. Results: The completion rate was 100% regardless of participant group without causing immediate fatigue. ME/CFS appeared to show a higher N-Acetylaspartate in L-DLPFC compared to HCs (OR = 8.49, p = 0.040), correlating with poorer fatigue, pain, and sleep quality scores (p's = 0.001-0.015). An increase in brain activation involving the frontal lobe and the brainstem was observed in ME/CFS compared to HCs (Z > 3.4, p's < 0.010). Conclusions: The study demonstrates the feasibility of combining MRS and fMRI to capture neurochemical and neurophysiological features of ME/CFS in female participants. Further research with larger cohorts of more representative sampling and follow-ups is needed to validate these apparent differences between ME/CFS and HCs.

Toward structure and metabolism of glycogen C1-C6 in humans at 7T by localized 13C MRS using low-power bilevel broadband 1H decoupling.

This work aims to develop and implement a pulse-acquire sequence for three-dimensional (3D) single-voxel localized 13C MRS in humans at 7T, in conjunction with bilevel broadband 1H decoupling, and to test its feasibility in vitro and in vivo in human calf muscle with emphasis on the detection of glycogen C1-C6. A localization scheme suitable for measuring fast-relaxing 13C signals in humans at 7T was developed and implemented using the outer volume suppression (OVS) and one-dimensional image selected in vivo spectroscopy (ISIS-1D) schemes, similar to that which was previously reported in humans at 4T. The 3D 13C localization scheme was followed by uniform 13C adiabatic excitation, all complemented with an option for bilevel broadband 1H decoupling to improve both 13C sensitivity and spectral resolution at 7T. The performance of the pulse-acquire sequence was investigated in vitro on phantoms and in vivo in the human calf muscle of three healthy volunteers, while measuring glycogen C1-C6. In addition, T1 and T2 of glycogen C1-C6 were measured in vitro at 7T, as well as T1 of glycogen C1 in vivo. The glycerol C2 and C1,3 lipid resonances were efficiently suppressed in vitro at 7T using the OVS and ISIS-1D schemes, allowing distinct detection of glycogen C2-C6. While some glycerol remained in calf muscle in vivo, the intense lipid at 130 ppm was efficiently suppressed. The 13C sensitivity and spectral resolution of glycogen C1-C6 in vitro and glycogen C1 in vivo were improved at 7T using bilevel broadband 1H decoupling. The T1 and T2 of glycogen C1-C6 in vitro at 7T were consistent compared with those at 8.5T, while the T1 of glycogen C1 in vivo at 7T resulted similar to that in vitro. Localized 13C MRS is feasible in human calf muscle in vivo at 7T, and this will allow further extension of this method for 13C MRS measurements such as in the brain.

Investigation of Creatine Levels in Glial Tumors Using MR Spectroscopy

Purpose: The present study examines the efficacy of Creatine (Cr) levels in the determination of tumor grade on single-voxel (SV) and multi-voxel (MV) magnetic resonance spectroscopy (MRS) in patients with glial tumors. Material and Methods: A retrospective review was made of 20 SV and 20 MV MRS PDF images of patients with a pathological diagnosis of glial tumor. Cr values and metabolite ratios were measured in the tumor and compared with those in the healthy symmetrical brain parenchyma of the contralateral hemisphere. Results: A significant difference was noted in the (Cho+Cr)/NAA and Cho/NAA ratios on SV MRS between the high-grade tumors and the healthy contralateral hemisphere. On MV MRS, Cho/NAA ratios within the minimum and maximum Cr(h) voxels (Cho/NAAmin-Cr(h), Cho/NAAmax-Cr(h), respectively) were higher in high-grade tumors compared to healthy tissue. ROC analysis showed that the max-Cr(h) metabolite on MV MRS was successful in distinguishing low-grade tumors from high-grade tumors. Conclusion: Using the minimum and maximum values of Cr as a reference can improve the overall diagnostic accuracy in the diagnosis and grading of glial tumors. Our findings showed that Cr tended to be low in high-grade tumors and further that the max-Cr(h) metabolite may help in the differentiation of glial tumors on MV MRS.

B0-insensitive image navigators for prospective motion-corrected MRS with localized second-order shimming.

Localized shimming in single-voxel MRS often results in large B0 inhomogeneity outside the volume-of-interest. This causes unacceptable degradation in motion navigator images. Switching back and forth between whole-brain shim and localized shim is possible for linear shims, but not for higher-order shims. Here we propose motion navigators largely insensitive to B0 inhomogeneity for prospective motion-corrected MRS with localized higher-order shimming. A recent fast high-resolution motion navigator based on spiral-in/out k-space trajectories and multislice-to-volume registration was modified by splitting the readout into multiple shot interleaves which shortened the echo time and reduced the effect of B0 inhomogeneity. The performance of motion correction was assessed in healthy subjects in the prefrontal cortex using a sLASER sequence at 3T (N = 5) and 7T (N = 5). With multiple spatial interleaves, excellent quality navigator images were acquired in the whole brain in spite of large B0 inhomogeneity outside the MRS voxel. The total duration of the navigator in sLASER remained relatively short even with multiple shots (3T: 10 spatial interleaves 94 ms per slice; 7T: 15 spatial interleaves 103 ms per slice). Prospective motion correction using the multi-shot navigators yielded comparable spectral quality (water linewidth and metabolite SNR) with and without subject motion. B0-insensitive motion navigators enable prospective motion correction for MRS with all first- and second-order shims adjusted in the MRS voxel, providing optimal spectral linewidth.

Preliminary study of proton magnetic resonance spectroscopy to assess bone marrow adiposity in the third metacarpus or metatarsus in Thoroughbred racehorses.

Magnetic resonance spectroscopy (MRS) has been used to investigate metabolic changes within human bone. It may be possible to use MRS to investigate bone metabolism and fracture risk in the distal third metacarpal/tarsal bone (MC/MTIII) in racehorses. To determine the feasibility of using MRS as a quantitative imaging technique in equine bone by using the 1H spectra for the MC/MTIII to calculate fat content (FC). Observational cross-sectional study. Limbs from Thoroughbred racehorses were collected from horses that died or were subjected to euthanasia on racecourses. Each limb underwent magnetic resonance imaging (MRI) at 3 T followed by single-voxel MRS at three regions of interest (ROI) within MC/MTIII (lateral condyle, medial condyle, proximal bone marrow [PBM]). Percentage FC was calculated at each ROI. Each limb underwent computed tomography (CT) and bone mineral density (BMD) was calculated for the same ROIs. All MR and CT images were graded for sclerosis. Histology slides were graded for sclerosis and proximal marrow space was calculated. Pearson or Spearman correlations were used to assess the relationship between BMD, FC and marrow space. Kruskal-Wallis tests were used to check for differences between sclerosis groups for BMD or FC. Eighteen limbs from 10 horses were included. A negative correlation was identified for mean BMD and FC for the lateral condyle (correlation coefficient = -0.60, p = 0.01) and PBM (correlation coefficient = -0.5, p = 0.04). There was a significant difference between median BMD for different sclerosis grades in the condyles on both MRI and CT. A significant difference in FC was identified between sclerosis groups in the lateral condyle on MRI and CT. Small sample size. 1H Proton MRS is feasible in the equine MC/MTIII. Further work is required to evaluate the use of this technique to predict fracture risk in racehorses.

Estimating the synaptic density deficit in Alzheimer's disease using multi-contrast CEST imaging.

In vivo noninvasive imaging of neurometabolites is crucial to improve our understanding of the underlying pathophysiological mechanism in neurodegenerative diseases. Abnormal changes in synaptic organization leading to synaptic degradation and neuronal loss is considered as one of the primary factors driving Alzheimer's disease pathology. Magnetic resonance based molecular imaging techniques such as chemical exchange saturation transfer (CEST) and magnetic resonance spectroscopy (MRS) can provide neurometabolite specific information which may relate to underlying pathological and compensatory mechanisms. In this study, CEST and short echo time single voxel MRS was performed to evaluate the sensitivity of cerebral metabolites to beta-amyloid (Aβ) induced synaptic deficit in the hippocampus of a mouse model of Alzheimer's disease. The CEST based spectra (Z-spectra) were acquired on a 9.4 Tesla small animal MR imaging system with two radiofrequency (RF) saturation amplitudes (1.47 μT and 5.9 μT) to obtain creatine-weighted and glutamate-weighted CEST contrasts, respectively. Multi-pool Lorentzian fitting and quantitative T1 longitudinal relaxation maps were used to obtain metabolic specific apparent exchange-dependent relaxation (AREX) maps. Short echo time (TE = 12 ms) single voxel MRS was acquired to quantify multiple neurometabolites from the right hippocampus region. AREX contrasts and MRS based metabolite concentration levels were examined in the ARTE10 animal model for Alzheimer's disease and their wild type (WT) littermate counterparts (age = 10 months). Using MRS voxel as a region of interest, group-wise analysis showed significant reduction in Glu-AREX and Cr-AREX in ARTE10, compared to WT animals. The MRS based results in the ARTE10 mice showed significant decrease in glutamate (Glu) and glutamate-total creatine (Glu/tCr) ratio, compared to WT animals. The MRS results also showed significant increase in total creatine (tCr), phosphocreatine (PCr) and glutathione (GSH) concentration levels in ARTE10, compared to WT animals. In the same ROI, Glu-AREX and Cr-AREX demonstrated positive associations with Glu/tCr ratio. These results indicate the involvement of neurotransmitter metabolites and energy metabolism in Aβ-mediated synaptic degradation in the hippocampus region. The study also highlights the feasibility of CEST and MRS to identify and track multiple competing and compensatory mechanisms involved in heterogeneous pathophysiology of Alzheimer's disease in vivo.

Getting the phase consistent: The importance of phase description in balanced steady-state free precession MRI of multi-compartment systems.

Determine the correct mathematical phase description for balanced steady-state free precession (bSSFP) signals in multi-compartment systems. Based on published bSSFP signal models, different phase descriptions can be formulated: one predicting the presence and the other predicting the absence of destructive interference effects in multi-compartment systems. Numerical simulations of bSSFP signals of water and acetone were performed to evaluate the predictions of these different phase descriptions. For experimental validation, bSSFP profiles were measured at 3T using phase-cycled bSSFP acquisitions performed in a phantom containing mixtures of water and acetone, which replicates a system with two signal components. Localized single voxel MRS was performed at 7T to determine the relative chemical shift of the acetone-water mixtures. Based on the choice of phase description, the simulated bSSFP profiles of water-acetone mixtures varied significantly, either displaying or lacking destructive interference effects, as predicted theoretically. In phantom experiments, destructive interference was consistently observed in the measured bSSFP profiles of water-acetone mixtures, supporting the theoretical description that predicts such interference effects. The connection between the choice of phase description and predicted observation enables unambiguous experimental identification of the correct phase description for multi-compartment bSSFP profiles, which is consistent with the Bloch equations. The study emphasizes that consistent phase descriptions are crucial for accurately describing multi-compartment bSSFP signals, as incorrect phase descriptions result in erroneous predictions.

Characterisation of paediatric brain tumours by their MRS metabolite profiles.

1H-magnetic resonance spectroscopy (MRS) has the potential to improve the noninvasive diagnostic accuracy for paediatric brain tumours. However, studies analysing large, comprehensive, multicentre datasets are lacking, hindering translation to widespread clinical practice. Single-voxel MRS (point-resolved single-voxel spectroscopy sequence, 1.5 T: echo time [TE] 23-37 ms/135-144 ms, repetition time [TR] 1500 ms; 3 T: TE 37-41 ms/135-144 ms, TR 2000 ms) was performed from 2003 to 2012 during routine magnetic resonance imaging for a suspected brain tumour on 340 children from five hospitals with 464 spectra being available for analysis and 281 meeting quality control. Mean spectra were generated for 13 tumour types. Mann-Whitney U-tests and Kruskal-Wallis tests were used to compare mean metabolite concentrations. Receiver operator characteristic curves were used to determine the potential for individual metabolites to discriminate between specific tumour types. Principal component analysis followed by linear discriminant analysis was used to construct a classifier to discriminate the three main central nervous system tumour types in paediatrics. Mean concentrations of metabolites were shown to differ significantly between tumour types. Large variability existed across each tumour type, but individual metabolites were able to aid discrimination between some tumour types of importance. Complete metabolite profiles were found to be strongly characteristic of tumour type and, when combined with the machine learning methods, demonstrated a diagnostic accuracy of 93% for distinguishing between the three main tumour groups (medulloblastoma, pilocytic astrocytoma and ependymoma). The accuracy of this approach was similar even when data of marginal quality were included, greatly reducing the proportion of MRS excluded for poor quality. Children's brain tumours are strongly characterised by MRS metabolite profiles readily acquired during routine clinical practice, and this information can be used to support noninvasive diagnosis. This study provides both key evidence and an important resource for the future use of MRS in the diagnosis of children's brain tumours.

Brain glutathione and GABA+ levels in autistic children.

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social communication challenges and repetitive behaviors. Altered neurometabolite levels, including glutathione (GSH) and gamma-aminobutyric acid (GABA), have been proposed as potential contributors to the biology underlying ASD. This study investigated whether cerebral GSH or GABA levels differ between a cohort of children aged 8-12 years with ASD (n = 52) and typically developing children (TDC, n = 49). A comprehensive analysis of GSH and GABA levels in multiple brain regions, including the primary motor cortex (SM1), thalamus (Thal), medial prefrontal cortex (mPFC), and supplementary motor area (SMA), was conducted using single-voxel HERMES MR spectroscopy at 3T. The results revealed no significant differences in cerebral GSH or GABA levels between the ASD and TDC groups across all examined regions. These findings suggest that the concentrations of GSH (an important antioxidant and neuromodulator) and GABA (a major inhibitory neurotransmitter) do not exhibit marked alterations in children with ASD compared to TDC. A statistically significant positive correlation was observed between GABA levels in the SM1 and Thal regions with ADHD inattention scores. No significant correlation was found between metabolite levels and hyper/impulsive scores of ADHD, measures of core ASD symptoms (ADOS-2, SRS-P) or adaptive behavior (ABAS-2). While both GSH and GABA have been implicated in various neurological disorders, the current study provides valuable insights into the specific context of ASD and highlights the need for further research to explore other neurochemical alterations that may contribute to the pathophysiology of this complex disorder.

Chronic neuropathic pain components in whiplash-associated disorders correlate with metabolite concentrations in the anterior cingulate and dorsolateral prefrontal cortex: a consensus-driven MRS re-examination.

Whiplash injury (WHI) is characterised by a forced neck flexion/extension, which frequently occurs after motor vehicle collisions. Previous studies characterising differences in brain metabolite concentrations and correlations with neuropathic pain (NP) components with chronic whiplash-associated disorders (WAD) have been demonstrated in affective pain-processing areas such as the anterior cingulate cortex (ACC). However, the detection of a difference in metabolite concentrations within these cortical areas with chronic WAD pain has been elusive. In this study, single-voxel magnetic resonance spectroscopy (MRS), following the latest MRSinMRS consensus group guidelines, was performed in the anterior cingulate cortex (ACC), left dorsolateral prefrontal cortex (DLPFC), and occipital cortex (OCC) to quantify differences in metabolite concentrations in individuals with chronic WAD with or without neuropathic pain (NP) components. Healthy individuals (n = 29) and participants with chronic WAD (n = 29) were screened with the Douleur Neuropathique 4 Questionnaire (DN4) and divided into groups without (WAD-noNP, n = 15) or with NP components (WAD-NP, n = 14). Metabolites were quantified with LCModel following a single session in a 3 T MRI scanner within the ACC, DLPFC, and OCC. Participants with WAD-NP presented moderate pain intensity and interference compared with the WAD-noNP group. Single-voxel MRS analysis demonstrated a higher glutamate concentration in the ACC and lower total choline (tCho) in the DLPFC in the WAD-NP versus WAD-noNP group, with no intergroup metabolite difference detected in the OCC. Best fit and stepwise multiple regression revealed that the normalised ACC glutamate/total creatine (tCr) (p = 0.01), DLPFC n-acetyl-aspartate (NAA)/tCr (p = 0.001), and DLPFC tCho/tCr levels (p = 0.02) predicted NP components in the WAD-NP group (ACC r 2 = 0.26, α = 0.81; DLPFC r 2 = 0.62, α = 0.98). The normalised Glu/tCr concentration was higher in the healthy than the WAD-noNP group within the ACC (p < 0.05), but not in the DLPFC or OCC. Neither sex nor age affected key normalised metabolite concentrations related to WAD-NP components when compared to the WAD-noNP group. This study demonstrates that elevated glutamate concentrations within the ACC are related to chronic WAD-NP components, while higher NAA and lower tCho metabolite levels suggest a role for increased neuronal-glial signalling and cell membrane dysfunction in individuals with chronic WAD-NP components.

Comparative Evaluation of Imaging Techniques for Paraspinal Muscle Fat Quantification

Introduction: Low back pain (LBP) is a prevalent health issue associated with morphological changes in paravertebral muscles. Magnetic resonance imaging (MRI) is effective in identifying muscle steatosis, with MR spectroscopy (MRS) considered the gold standard. However, MRS is limited by technical challenges, prompting interest in Dixon sequences for fat quantification. Materials and Methods: We conducted a study comparing Multi Echo VIBE Dixon with single-voxel MR spectroscopy in quantifying fat fractions in lumbar multifidus muscles of chronic LBP patients. Ninety-eight measurements from 49 patients were analysed. Qualitative and quantitative image analyses were performed, and statistical analysis was conducted using SPSS 27. Results: Significant positive correlation (correlation coefficient: 0.992, p &lt; 0.001) was found between Dixon and MRS fat fraction measurements. Intra-class correlation coefficient was 0.991 (p &lt; 0.001), indicating strong agreement. No proportion bias was observed. Factors such as age, sex, and spinal degeneration correlated positively with multifidus fat atrophy. Conclusion: T2*-corrected Dixon imaging aligns well with spectroscopic measurements, offering an accurate alternative for estimating paraspinal muscle fat content in chronic LBP patients. Further studies are needed to establish threshold values for Dixon imaging. Chronic LBP is associated with multifidus muscle atrophy and fat infiltration, highlighting the need for effective management strategies.

Metabolite profile in hereditary spastic paraplegia analyzed using magnetic resonance spectroscopy: a cross-sectional analysis in a longitudinal study.

Hereditary Spastic Paraplegias (HSP) are genetic neurodegenerative disorders affecting the corticospinal tract. No established neuroimaging biomarker is associated with this condition. A total of 46 patients affected by HSP, genetically and clinically evaluated and tested with SPRS scores, and 46 healthy controls (HC) matched by age and gender underwent a single-voxel Magnetic Resonance Spectroscopy sampling (MRS) of bilateral pre-central and pre-frontal regions. MRS data were analyzed cross-sectionally (at T0 and T1) and longitudinally (T0 vs. T1). Statistically significant data showed that T0 mI/Cr in the pre-central areas of HSP patients was higher than in HC. In the left (L) pre-central area, NAA/Cr was significantly lower in HSP than in HC. In the right (R) pre-frontal area, NAA/Cr was significantly lower in HSP patients than in HC. HSP SPG4 subjects had significantly lower Cho/Cr concentrations in the L pre-central area compared to HC. Among the HSP subjects, non-SPG4 patients had significantly higher mI/Cr in the L pre-central area compared to SPG4 patients. In the R pre-frontal area, NAA/Cr was reduced, and ml/Cr was higher in non-SPG4 patients compared to SPG4 patients. Comparing "pure" and "complex" forms, NAA/Cr was higher in pHSP than in cHSP in the R pre-central and R pre-frontal areas. The longitudinal analysis, which involved fewer patients (n = 30), showed an increase in mI/Cr concentration in the L pre-frontal area among HSP subjects with respect to baseline. The patients had significantly higher SPRS scores at follow-up, with a significant positive correlation between SPRS scores and mI/Cr in the L pre-central area, while in bilateral pre-frontal areas, lower SPRS scores corresponded to higher NAA/Cr concentrations. To explore the discriminating power of MRS in correctly identifying HSP and controls, an inference tree methodology classified HSP subjects and controls with an overall accuracy of 73.9%, a sensitivity of 87.0%, and a specificity of 60.9%. This pilot study indicates that brain MRS is a valuable approach that could potentially serve as an objective biomarker in HSP.

Bone Marrow Adiposity Alterations in Type 2 Diabetes Are Sex-Specific and Associated with Serum Lipid Levels.

Type 2 diabetes (T2D) has negative effects on skeletal health. A proposed mechanism of diabetic bone disease connects hyperlipidemia to increased bone marrow adiposity and decreased bone quality. Previous research on Type 1 diabetes reported positive associations between serum lipid levels and marrow adiposity, but no data exist for T2D. In addition, marrow adiposity is sex-dependent in healthy populations, but sex has not been addressed adequately in previous reports of marrow adiposity in T2D. The purpose of this study was to quantify associations of marrow adiposity and composition with T2D status, serum lipid levels, and sex. T2D patients and normoglycemic controls (n = 39/37) were included. Single-voxel magnetic resonance spectroscopy (MRS) was performed at the spine and tibia. Quantitative MRS outcomes of marrow adiposity and composition were calculated. Linear regression models were used to compare MRS outcomes among groups and to evaluate associations of MRS outcomes with serum lipid levels. All analyses were performed on sex-stratified subgroups. Total, unsaturated, and saturated fat content at the spine were lower in T2D participants compared to controls in age-adjusted models; these differences were significant in men but not in women. In our study cohort, total cholesterol, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) were lower in T2D participants compared to controls. Adjustment for LDL, HDL, and statin use attenuated the association of T2D status with unsaturated fat but not saturated fat in men. Further analysis confirmed significant associations between serum lipid levels and MRS outcomes. Specifically, we found a positive association between LDL cholesterol and total marrow fat in the male T2D group and a negative association between HDL and total marrow fat in the female T2D group. In conclusion, our results suggest that marrow adiposity and composition are associated with lipid levels as well as T2D status, and these relationships are sex-specific. © 2023 American Society for Bone and Mineral Research (ASBMR).

Validity of an automated screening Dixon technique for quantifying hepatic steatosis in living liver donors.

This retrospective study aimed to evaluate the validity of an automated screening Dixon (e-DIXON) technique for quantifying hepatic steatosis in living liver-donor patients by comparison with magnetic resonance spectroscopy (MRS) as a reference standard. A total of 285 living liver-donor candidates were examined with the e-DIXON technique and single-voxel MRS to assess hepatic steatosis and iron deposition between January 2014 and February 2019. The sensitivity, specificity, and positive and negative predictive values (PPV and NPV) of the e-DIXON technique for hepatic steatosis were calculated. The mean fat signal fractions obtained in MRS were compared between the donors diagnosed with hepatic steatosis and the normal group. The mean R2 values of donors with or without hepatic siderosis also were compared. The e-DIXON technique diagnosed normal in 133 (47%), fat in 124 (44%), iron in one (0.4%), and a combination of both fat and iron in 27 (10%) donors. The sensitivity, specificity, PPV, and NPV ​​for diagnosing hepatic steatosis were 94%, 70%, 64%, and 96%, respectively. There was a significant difference in the mean fat signal fraction obtained in MRS between the steatosis and normal groups (p < 0.001), but R2 values were not significantly different between siderosis and normal groups (p = 0.11). The e-DIXON technique showed a strong correlation with MRS in fat measurement (r2 = 0.92, p < 0.001). The e-DIXON technique reliably screens for hepatic steatosis but may not accurate for detecting hepatic iron deposition.

Prospective motion correction for cervical spinal cord MRS.

To develop prospective motion correction for single-voxel MRS in the human cervical spinal cord. A motion MR navigator was implemented using reduced field-of-view 2D-selective RF excitation together with EPI readout. A short-echo semi-LASER sequence (TE = 30 ms) was updated to incorporate this real-time image-based motion navigator, as well as real-time shim and frequency navigators. Five healthy participants were studied at 3 T with a 64-channel head-neck receive coil. Single-voxel MRS data were measured in a voxel located at the C3-5 vertebrae level. The motion navigator was used to correct for translations in the X-Y plane and was validated by assessing spectral quality with and without prospective correction in the presence of subject motion. Without prospective correction, motion resulted in severe lipid contamination in the MR spectra. With prospective correction, the quality of spinal cord MR spectra in the presence of motion was similar to that obtained in the absence of motion, with comparable spectral signal-to-noise ratio and linewidth and no significant lipid contamination. Prospective motion and B0 correction allow acquisition of good-quality MR spectra in the human cervical spinal cord in the presence of motion. This new technique should facilitate reliable acquisition of spinal cord MR spectra in both research and clinical settings.

Magnetic resonance spectroscopy (MRS) of multifidus muscle metabolites in chronic low back pain (CLBP).

The purpose of the study was to investigate several potential imaging biomarkers of CLBP that may be useful for diagnosis and treatment efficacy evaluation. Proton magnetic resonance spectroscopy (1H-MRS) was used to detect the content and ratio of creatine (Cr), choline (Cho), and lipid (Lip) in the multifidus muscle (Mm) in patients with CLBP and to test for relationships between these metabolites and pain severity and duration. Sixty patients with CLBP (experimental group) and sixty-nine asymptomatic volunteers (control group) underwent routine diagnostic magnetic resonance imaging of the lumbar spine. 1H-MRS was acquired with single-voxel MR spectroscopy. The MRS region of interest for measuring Cho, Cr, and Lip concentrations was determined at the L4/5 multifidus muscle (Mm), bilaterally. The contents and ratios of Cr, Cho, and Lip in bilateral and ipsilateral-to-pain (or matched control side) Mm were obtained, and the integral ratios of different metabolites obtained by using Cr as an internal reference were statistically analyzed. There were no significant within-group differences in the contents and ratios of Lip, Cr, Cho, Lip/Cr, and Cho/Cr between the left and right Mm of the healthy control group (p > 0.05) or the CLBP group (p > 0.05). The CLBP group showed a much higher Lip and Lip/Cr ratio in the bilateral Mm compared to the healthy control group (p < 0.05) but there were no between-group differences in Cr, Cho, or the Cho/Cr ratio (p > 0.05). The severity of CLBP was correlated with Lip (p < 0.05). Using 1H-MRS, we demonstrated higher Lip and Lip/Cr ratios in the Mm of patients with CLBP, compared to asymptomatic controls. Mm Lip was correlated with CLBP intensity. An increase in Lip in the Mm may be a characteristic finding in CLBP and may offer a useful prognostic marker for guiding rehabilitation strategies.